Cardiopulmonary resuscitation, commonly known as CPR,[1] is an emergency procedure performed in an effort to manually preserve intact brain function until further measures are taken to restore spontaneous blood circulation and breathing in a person who is in cardiac arrest. It is indicated in those who are unresponsive with no breathing or abnormal breathing, for example, agonal respirations.

According to the International Liaison Committee on Resuscitation guidelines, CPR involves chest compressions at least Script error: No such module "convert". deep and at a rate of at least 100 per minute in an effort to create artificial circulation by manually pumping blood through the heart and thus the body. The rescuer may also provide breaths by either exhaling into the subject's mouth or nose or using a device that pushes air into the subject's lungs. This process of externally providing ventilation is termed artificial respiration. Current recommendations place emphasis on high-quality chest compressions over artificial respiration; a simplified CPR method involving chest compressions only is recommended for untrained rescuers.

Medical uses

CPR is indicated for any person unresponsive with no breathing or breathing only in occasional agonal gasps, as it is most likely that they are in cardiac arrest.[2]:S643 If a person still has a pulse but is not breathing (respiratory arrest) artificial respirations may be more appropriate, but, due to the difficulty people have in accurately assessing the presence or absence of a pulse, CPR guidelines recommend that lay persons should not be instructed to check the pulse, while giving healthcare professionals the option to check a pulse.[3] In those with cardiac arrest due to trauma CPR is considered futile but still recommended.[4] Correcting the underlying cause such as a pneumothorax or pericardial tamponade may help.[4]

Methods

CPR training: CPR is being administered while a second rescuer prepares for defibrillation.

In 2010, the American Heart Association and International Liaison Committee on Resuscitation updated their CPR guidelines.[2]:S640[5] The importance of high quality CPR (sufficient rate and depth without excessively ventilating) was emphasized.[2]:S640 The order of interventions was changed for all age groups except newborns from airway, breathing, chest compressions (ABC) to chest compressions, airway, breathing (CAB).[2]:S642 An exception to this recommendation is for those believed to be in a respiratory arrest (drowning, etc.).[2]:S642 The most important aspect of CPR are: few interruptions of chest compressions, a sufficient speed and depth of compressions, completely relaxing pressure between compressions, and not ventilating too much.[6] It is unclear if a few minutes of CPR before defibrillation results in different outcomes than immediate defibrillation.[7]

Standard

A universal compression to ventilation ratio of 30:2 is recommended by the AHA.[8]:8 With children, if at least 2 trained rescuers are present a ratio of 15:2 is preferred.[8]:8 In newborns a rate of 3:1 is recommended unless a cardiac cause is known in which case a 15:2 ratio is reasonable.[2]:S647 If an advanced airway such as an endotracheal tube or laryngeal mask airway is in place, artificial ventilation should occur without pauses in compressions at a rate of 8–10 per minute.[9] The recommended order of interventions is chest compressions, airway, breathing or CAB in most situations,[2]:S642 with a compression rate of at least 100 per minute in all groups.[8]:8 Recommended compression depth in adults and children is at least 5 cm (2 inches) and in infants it is Script error: No such module "convert"..[8]:8 As of 2010 the Resuscitation Council (UK) still recommends ABC for children.[10] As it can be difficult to determine the presence or absence of a pulse, the pulse check has been removed for lay providers and should not be performed for more than 10 seconds by healthcare providers.[8]:8 In adults, rescuers should use two hands for the chest compressions, while in children they should use one, and with infants two fingers (index and middle fingers).[11]

Compression only

Compression-only (hands-only or cardiocerebral resuscitation) CPR is a technique that involves chest compressions without artificial respiration.[2]:S643 It is recommended as the method of choice for the untrained rescuer or those who are not proficient because it is easier to perform and instructions are easier to give over a phone.[2]:S643[8]:8[12] In adults with out-of-hospital cardiac arrest, compression-only CPR by the lay public has a higher success rate than standard CPR.[12] The exceptions are cases of drownings, drug overdose and arrest in children. Children who receive compression-only CPR have the same outcomes as those having received no CPR.[2]:S646 The method of delivering chest compressions remains the same, as does the rate (at least 100 per minute). It is hoped that the use of compression-only delivery will increase the chances of the lay public delivering CPR.[13] As per the American Heart Association, the beat of the Bee Gees song "Stayin' Alive" provides an ideal rhythm in terms of beats per minute to use for hands-only CPR.[14] One can also hum Queen's "Another One Bites The Dust", which is exactly 100 beats-per-minute and contains a memorable repeating drum pattern.[15] For those with non cardiac arrest and people less than 20 years of age, standard CPR is superior to compression-only CPR.[16][17]

Prone CPR

Simultaneous maintenance of blood circulation and ventilation can be obtained by compressing the back if the victim is in prone position, by turning the head to the side and compressing the back. Due to the head's being turned, the risk of vomiting and complications caused by aspiration pneumonia is significantly reduced, and the method means the patient continues to get air into their lungs without the need for mouth-to-mouth respiration.[18]

Pregnancy

During pregnancy when a woman is lying on her back, the uterus may compress the inferior vena cava and thus decrease venous return.[4] It is therefore recommended that the uterus be pushed to the woman's left; if this is not effective, either roll the woman 30° or healthcare professionals should consider emergency Caesarean section.[4]

Other

Interposed abdominal compressions may be beneficial in the hospital environment.[19] There is no evidence of benefit pre-hospital or in children.[19]

Cooling during CPR is being studied as currently results are unclear whether or not it improves outcomes.[20]

Internal cardiac massage is manual squeezing of the exposed heart itself carried out through a surgical incision into the chest cavity, usually when the chest is already open for cardiac surgery.

CPR serves as the foundation of successful cardiopulmonary resuscitation, preserving the body for defibrillation and advanced life support. Even in the case of a "non-shockable" rhythm, such as Pulseless Electrical Activity (PEA) where defibrillation is not indicated, effective CPR is no less important. Used alone, CPR will result in few complete recoveries, though the outcome without CPR is almost uniformly fatal.[24]

Studies have shown that immediate CPR followed by defibrillation within 3–5 minutes of sudden VF cardiac arrest dramatically improves survival. In cities such as Seattle where CPR training is widespread and defibrillation by EMS personnel follows quickly, the survival rate is about 20 percent for all causes and as high as 57 percent if a witnessed "shockable" arrest.[25] In cities such as New York, without those advantages, the survival rate is only 5 percent for witnessed shockable arrest.[26]

Compression-only CPR may be less effective in children than in adults, as cardiac arrest in children is more likely to have a non-cardiac cause. In a 2010 prospective study of cardiac arrest in children (age 1–17) for arrests with a non-cardiac cause, provision by bystanders of conventional CPR with rescue breathing yielded a favorable neurological outcome at one month more often than did compression-only CPR (OR 5.54; 95% confidence interval 2.52–16.99). For arrests with a cardiac cause in this cohort, there was no difference between the two techniques (OR 1.20; 95% confidence interval 0.55–2.66).[27] This is consistent with American Heart Association guidelines for parents.[28]

There is a higher proportion of patients who achieve spontaneous circulation (ROSC), where their heart starts beating on its own again, than ultimately survive to be discharged from hospital (see table above). This may be due to medical staff being ultimately unable to address the cause of the cardiac arrest, to other co-morbidities, or to the patient being gravely ill in more than one way. Ultimately, only 5–10% of patients in cardiac arrest will survive after an attempted resuscitation.[29]

Pathophysiology

CPR is used on people in cardiac arrest in order to oxygenate the blood and maintain a cardiac output to keep vital organs alive. Blood circulation and oxygenation are required to transport oxygen to the tissues. The physiology of CPR involves generating a pressure gradient between the arterial and venous vascular beds; CPR achieves this via multiple mechanisms [30] The brain may sustain damage after blood flow has been stopped for about four minutes and irreversible damage after about seven minutes.[31][32][33][34][35] Typically if blood flow ceases for one to two hours, then body cells die. Therefore, in general CPR is effective only if performed within seven minutes of the stoppage of blood flow.[36] The heart also rapidly loses the ability to maintain a normal rhythm. Low body temperatures, as sometimes seen in near-drownings, prolong the time the brain survives. Following cardiac arrest, effective CPR enables enough oxygen to reach the brain to delay brain stem death, and allows the heart to remain responsive to defibrillation attempts.

The most common injuries sustained from CPR are rib fractures, with literature suggesting an incidence between 13% and 97%, and sternal fractures, with an incidence between 1% to 43%.[43] Whilst these iatrogenic injuries can require further intervention (assuming the patient survives the cardiac arrest), only 0.5% of them are life-threatening in their own right.[42]

The type and frequency of injury can be affected by factors such as gender and age. For instance, women have a higher risk of sternal fractures than men, and risk for rib fractures increases significantly with age.[44] Children and infants have a low risk of rib fractures during CPR, with an incidence less than 2%, although, when they do occur, they are usually anterior and multiple.[43][45][46]

Where CPR is performed in error by a bystander, on a patient not in cardiac arrest, only around 2% suffer injury as a result (although 12% experienced discomfort).[47]

Adjunct devices

While several adjunctive devices are available, none other than defibrillation, as of 2010, have consistently been found to be better than standard CPR for out-of-hospital cardiac arrest.[2]:S644 These devices can be split into three broad groups: timing devices' those that assist the rescuer to achieve the correct technique,especially depth and speed of compressions; and those that take over the process completely.

Timing devices

Timing devices can feature a metronome (an item carried by many ambulance crews) in order to assist the rescuer in achieving the correct rate. Some units can also give timing reminders for performing compressions, ventilating and changing operators.[48]

Manual assist devices

Mechanical devices have not been found to have greater benefit than harm and thus are not currently recommended for widespread use.[49]

Audible and visual prompting may improve the quality of CPR and prevent the decrease of compression rate and depth that naturally occurs with fatigue,[50][51][52][53][54][55] and to address this potential improvement, a number of devices have been developed to help improve CPR technique.

These items can be devices to placed on top of the chest, with the rescuer's hands going over the device, and a display or audio feedback giving information on depth, force or rate,[56] or in a wearable format such as a glove.[57] Several published evaluations show that these devices can improve the performance of chest compressions.[58][59]

As well as its use during actual CPR on a cardiac arrest victim, which relies on the rescuer carrying the device with them, these devices can also be used as part of training programs to improve basic skills in performing correct chest compressions.[60]

Automatic devices

There are also some automated devices available that take over the chest compressions for the rescuer. These have several advantages: they allow rescuers to focus on performing other interventions; they do not fatigue and begin to perform less effective compressions, as humans do; they are able to perform effective compressions in limited-space environments such as air ambulances, where manual compressions are difficult, and they allow ambulance workers to be strapped in safely rather than standing over a patient in a speeding vehicle. These devices use either pneumatic (high-pressure gas) or electrical power sources to drive a compressing pad on to the chest of the patient. One such device, known as the LUCAS, was developed at the University Hospital of Lund, is powered by the compressed oxygen supplies already standard in ambulances and hospitals, and has undergone numerous clinical trials, showing a marked improvement in coronary perfusion pressure[61] and return of spontaneous circulation.[62]

In August 2013, a 41-year-old woman living in a town near Melbourne in Australia was treated with the LUCAS device for 53 minutes while a stent was placed in an artery near her heart, clearing a 100% blockage. She was considered to be clinically dead for 40 minutes. She was discharged from the hospital a week later.[63]

Artificial ventilation can be achieved with multiple devices. While manual bag valve mask devices supply oxygen-enriched air through a facial mask (without maintaining an open airway), automatic devices utilize an oropharyngeal airway (e.g., Bergman or Guedel airways), which ensures airway patency. They also have a nozzle for the rescuer with a protective mask mode, preventing any mouth-to-mouth contact. Another system called the AutoPulse is electrically powered and uses a large band around the patient's chest that contracts rhythmically in order to deliver chest compressions. This is also backed by clinical studies showing increased rates of return of spontaneous circulation.[64][65]

Mobile apps

To support training and incident management mobile apps have been published on the largest app markets. An evaluation of 61 available apps has revealed that a large amount does not follow international guidelines for basic-life support and many apps are not designed in a user-friendly way.[66]

Prevalence

Chance of receiving CPR

Various studies suggest that in out-of-home cardiac arrest, bystanders, lay persons or family members attempt CPR in between 14%[67] and 45%[68] of the time, with a median of 32%.[69] Internationally, rates of bystander CPR reported to be as low as 1% and as high as 44%.[70] However, the effectiveness of this CPR is variable, and the studies suggest only around half of bystander CPR is performed correctly.[71][72] A recent study has shown that members of the public having received CPR training in the past lack the skills and confidence needed to save lives. These experts believe that better training is needed to improve the willingness to respond to cardiac arrest.[69]

There is a clear correlation between age and the chance of CPR being commenced. Younger people are far more likely to have CPR attempted on them before the arrival of emergency medical services.[67][73] It was also found that bystanders more commonly administer CPR when in public than when at the patient's home, although health care professionals are responsible for more than half of out-of-hospital resuscitation attempts.[68] People with no connection to the victim are more likely to perform CPR than are a member of their family.[74]

There is also a clear correlation between cause of arrest and the likelihood of a bystander initiating CPR. Lay persons are most likely to give CPR to younger cardiac arrest victims in a public place when it has a medical cause; victims in arrest from trauma, exsanguination or intoxication are less likely to receive CPR.[74]

Finally, it has been claimed that there is a higher chance that CPR will performed if the bystander is told to perform only the chest compression element of the resuscitation.[13]

Chance of receiving CPR in time

CPR is likely to be effective only if commenced within 6 minutes after the blood flow stops[75] because permanent brain cell damage occurs when fresh blood infuses the cells after that time, since the cells of the brain become dormant in as little as 4–6 minutes in an oxygen deprived environment and, therefore, cannot survive the reintroduction of oxygen in a traditional resuscitation. Research using cardioplegic blood infusion resulted in a 79.4% survival rate with cardiac arrest intervals of 72±43 minutes, traditional methods achieve a 15% survival rate in this scenario, by comparison. New research is currently needed to determine what role CPR, electroshock, and new advanced gradual resuscitation techniques will have with this new knowledge.[76]

A notable exception is cardiac arrest that occurs in conjunction with exposure to very cold temperatures. Hypothermia seems to protect by slowing down metabolic and physiologic processes, greatly decreasing the tissues' need for oxygen.[77] There are cases where CPR, defibrillation, and advanced warming techniques have revived victims after substantial periods of hypothermia.[78]

Society and culture

Portrayed effectiveness

CPR is often severely misrepresented in movies and television as being highly effective in resuscitating a person who is not breathing and has no circulation.

A 1996 study published in the New England Journal of Medicine showed that CPR success rates in television shows was 75% for immediate circulation, and 67% survival to discharge.[79][80] This gives the general public an unrealistic expectation of a successful outcome.[79] When educated on the actual survival rates, the proportion of patients over 60 years of age desiring CPR should they suffer a cardiac arrest drops from 41% to 22%.[81]

Stage CPR

Chest compressions are capable of causing significant local blunt trauma, including bruising or fracture of the sternum or ribs.[82] Performing CPR on a healthy person may or may not disrupt normal heart rhythm, but regardless the technique should not be performed on a healthy person because of the risk of trauma.

The portrayal of CPR technique on television and film often is purposely incorrect. Actors simulating the performance of CPR may bend their elbows while appearing to compress, to prevent force from reaching the chest of the actor portraying the victim.

Self-CPR hoax

A form of "self-CPR" termed "cough CPR" was the subject of a hoaxchain e-mail entitled "How to Survive a Heart Attack When Alone," which wrongly cited "ViaHealth Rochester General Hospital" as the source of the technique. Rochester General Hospital has denied any connection with the technique.[83][84]

"Cough CPR" in the sense of resuscitating oneself is impossible because a prominent symptom of cardiac arrest is unconsciousness,[85] in which case coughing is impossible, although myocardial infarction (heart attack) may occur to give rise to the cardiac arrest, so a patient may not be immediately unconscious. However, the vast majority of people suffering chest pain from a heart attack will not be in cardiac arrest and CPR is not needed to begin with. In these cases, attempting "cough CPR" will increase the workload on the heart and may be harmful.

The American Heart Association (AHA) and other resuscitation bodies[86] do not endorse "cough CPR", which it terms a misnomer as it is not a form of resuscitation. The AHA does recognize a limited legitimate use of the coughing technique: "This coughing technique to maintain blood flow during brief arrhythmias has been useful in the hospital, particularly during cardiac catheterization. In such cases the patient's ECG is monitored continuously, and a physician is present."[87] When coughing is used on trained and monitored patients in hospitals, it has been shown to be effective only for 90 seconds.[86]

CPR learned from movies and television

In at least one case, it has been alleged that CPR learned from a movie was used to save a person's life. In April 2011, it was claimed that nine-year-old Tristin Saghin saved his sister's life by administering CPR on her after she fell into a swimming pool, using only the knowledge of CPR that he had gleaned from a motion picture, Black Hawk Down.[88]

Hands-Only CPR portrayed as more palatable version

Less than 1/3 of those people who experience a cardiac arrest at home, work or in a public location have CPR performed on them. Most bystanders are worried that they might do something wrong.[89] On October 28, 2009 The American Heart Association and the Ad Council launched a Hands-Only CPR public service announcement and website as a means to address this issue.[90] In July 2011, new content was added to the website including a digital app that helps a user learn how to perform Hands-Only CPR.[91]

History

In the 19th century, Doctor H. R. Silvester described a method (The Silvester Method) of artificial respiration in which the patient is laid on their back, and their arms are raised above their head to aid inhalation and then pressed against their chest to aid exhalation.[92] The procedure is repeated sixteen times per minute. This type of artificial respiration is occasionally seen in films made in the early 20th century.

A second technique, called the Holger Nielsen technique, described in the first edition of the Boy Scout Handbook in the United States in 1911, was a form of artificial respiration where the person was laid face down, with their head to the side, resting on the palms of both hands. Upward pressure applied at the patient’s elbows raised the upper body while pressure on their back forced air into the lungs, in essence the Silvester Method with the patient flipped over. This form is seen well into the 1950s (it is used in an episode of Lassie during the mid-1950s), and was often used, sometimes for comedic effect, in theatrical cartoons of the time (see Tom and Jerry's "The Cat and the Mermouse" [1949]). This method would continue to be shown, for historical purposes, side-by-side with modern CPR in the Boy Scout Handbook until its ninth edition in 1979. The technique was later banned from first-aid manuals in the UK.

Similar techniques were described in early 20th century ju-jutsu and judo books, as being used as far back as the early 17th century. A New York Times correspondent reported those techniques being used successfully in Japan in 1910. In ju-jutsu (and later on, judo) those techniques were called Kappo or Kutasu.[93][94][95][96]

However, it was not until the middle of the 20th century that the wider medical community started to recognize and promote artificial respiration combined with chest compressions as a key part of resuscitation following cardiac arrest. The combination was first seen in a 1962 training video called "The Pulse of Life" created by James Jude, Guy Knickerbocker and Peter Safar. Jude and Knickerbocker, along with William Kouwenhoven and Joseph S. Redding had recently discovered the method of external chest compressions, whereas Safar had worked with Redding and James Elam to prove the effectiveness of artificial respiration. It was at Johns Hopkins University where the technique of CPR was originally developed. The first effort at testing the technique was performed on a dog by Redding, Safar and JW Perason. Soon afterward, the technique was used to save the life of a child.[97] Their combined findings were presented at the annual Maryland Medical Society meeting on September 16, 1960 in Ocean City, and gained widespread acceptance over the following decade, helped by the video and speaking tour they undertook. Peter Safar wrote the book ABC of Resuscitation in 1957. In the U.S., it was first promoted as a technique for the public to learn in the 1970s.[98]

Artificial respiration was combined with chest compressions based on the assumption that active ventilation is necessary to keep circulating blood oxygenated, and the combination was accepted without comparing its effectiveness with chest compressions alone. However, research over the past decade has shown that assumption to be in error, resulting in the AHA's acknowledgment of the effectiveness of chest compressions alone (see Compression only in this article).[99]

CPR has continued to advance, with recent developments including an emphasis on constant, rapid heart stimulation, and a de-emphasis on the respiration aspect. Studies have shown that people who had rapid, constant heart-only chest compression are 22% more likely to survive than those receiving conventional CPR that included breathing. What's more, because people tend to be reluctant to do mouth-to-mouth, chest-only CPR nearly doubles the chances of survival overall, by increasing the odds of receiving CPR in the first place.[100]

Administering CPR to animals

It is feasible to perform CPR on animals, including cats and dogs. The principles and practices are virtually identical to CPR for humans, except that resuscitation is usually done through the animal's nose, not the mouth. CPR should only be performed on unconscious animals to avoid the risk of being bitten; a conscious animal would not require chest compressions. Animals, depending on species, may have a lower bone density than humans and so CPR can cause bones to become weakened after it is performed.[101]

^(), "European Resuscitation Council (2005). "Part 2: Adult basic life support". Guidelines for resuscitation. The following is a summary of the evidence-based recommendations for the performance of basic life support: Rescuers begin CPR if the victim is unconscious, not moving, and not breathing (ignoring occasional gasps).[...]

^USA TodayAmerican Heart Association revises CPR guidelines An analysis of 3,700 cardiac arrests published Friday in the journal Lancet found that hands-only CPR saved 22% more lives than the conventional method. All told, the switch could save up to 3,000 additional lives a year in the USA and 5,000 to 10,000 in North America and Europe, says lead author Peter Nagele of Washington University in St. Louis.
A landmark study published Oct. 6 in The Journal of the American Medical Associationfound that bystanders who applied hands-only CPR were able to boost survival to 34% from 18% for those who got conventional CPR or none at all. In addition, the percentage of people willing to provide CPR rose from 28% in 2005 to 40% in 2009.